Air heating



Patented Oct. 4, 1932 UNITED STATES PATENT iazze CHARLES W. ANDREWS AND ALBERT J'. HULSE, OF CHICAGO, ILLINOIS, ASSIGNORS TO H. A. BRASSERT & COMPANY, OF CHICAGO, ILLINOIS, A CORPORATION OE ILLINOIS AIR HEATING- Application led March 22, 14928. Serial No. 263,947.

This invention relates to a new and -improved method ofheating air, and more particularly of heating the 'blast air for blast furnaces.

At the present time a blastfurnace is usually equipped with either Vthree or four air heating stoves, usually the latter.v Three of these stoves are normally being heated by gas, and the fourth is in;turn,l1eating-the incoming cold air. A `by-pass 'connection from the cold main to the hot main, controlled by what is `known as a mixing valve, is in general use in order that the temperature of the air going to the furnace maybe maintained fairly uniform. This is necessary as the stove when first put on air is very hot and gradually cools down vas the cold air absorbs heat from it. Likewise when the stove isI being heated by burning gas, the temperature of the outgoing" products of combustion,graduallyrises until at the end ofthe heating periodl the temperature may be around 1000o or 172000, whereas on the start it is often as low as 400? to 5000.

The stack temperature where two 'or three stoves are being heated, remains-practically constant at around 600O to 700 and often reaches 800O where high heats are being carried on the furnace.

According'to4 the method .of our invention a. recuperator is interposed between the stoves and stack and a portion ofthe heat going to the stack is recovered by air going to the stoves, or to the blast furnace. l/Vhe're such a recuperator is used, it will become possibleto permit the products of combustion to leave the stoves at a highertemperaf ture thaniin usual practice, since aV considerable portion of the remaining heat may be recovered in the recuperator.,`

It is well known that the amount offheat which can be put into the blasting air by a,

stove is in direct proportion to he heat in n the brickwork pf the, stove,` By oury invention the temperature of the stove and consequently the heat therein, may be increased, without increased `loss Vof'heat' to the4 stack, as Awould be the case in ordinary methods of operation with usualstoves. `The-heat head in the lstove is thus lincreased and such porstoves nowin use are not of sufficient sizeto give higher temperatures without undue vloss of efficiency dueto high stack temperatures.

There have been various, recent develop? ments in gas cleaning apparatus, including the introduction of the vortex types of ydry cleaners for. removing dust` from the blast furnace gas to be used in heating stoves or for other purposes; It is important in the use of our invention that the gas be cleaned so as not to depesit'dirt in the stoves or more particularly in therecuperator.V y The particular methods or apparatusused for cleaning the gas form no part of the present in` vention, butfor efficient operationl of our method, it is desirable that the gas be cleaned so as to contain not more than .05 grains per cubic foot. With `dirty gas there will be such Vdeposits in the recuperator as to "ad- Y fer.Y

It is an object of our invention to provide a new and improved method of heating air,

`particularly for blast furnaces or the like.

lIt is a further object to provide a method whereby increased temperatures may be secured without undue loss of heat through the stack.

od whereby the temperature of the hot blast versely affect the efficiency of the heat trans- Itis an additional object to provide a methv may be adequately controlled throughout the l cycle ofoperation without undue heat losses.A

L It is also an object to provide a method whichmay be adaptedto existing stoves by the'addition of suitable apparatus and thereby raise the temperature of the blastsupplied by said stoves.

' Other and further objects will appear as the description proceeds. Y

V7e have illustrated somewhat diagramma-tically in the accompanying drawings one lpreferred embodimentof vapparatus for carof the drawing is a diagrammatic showing of a construction adapted for carrying out our invention, certain parts beingV shown in section.

The cold blast main 11k is connected to the portion 12 of the recuperator 13, this portion 12 being also connected through the passage 14 with the secondary cold blast main 15. The connection between the passage 14 and the passage 15 vis controlled by valve 16. The passage 14 is also connected by means of passage 17 with the h'ot blast main 18, this connection being controlled by valve 19. The cold blast main 11 is also cross-connected by valve 21. i Y

The secondary main 15 is connected to the hot blastl stoves 22, 23, 24 and2/5 by means of passages26, 27, 28 and 29 which are controlled by valves 30, 31, 32 and 33, respectively. Y The stoves 22, 23,24 and 25 are connected to the hot blast main 18 by passages34,35,36 and 37, controlled by valves 38, 39, 40 and 41, respectively.` The stoves 22, 23, 24 and 25 are connected tothe outgoing iiue 42 by means of `trolled by the mixing valve 56.V

.passages 43, 44, 45 and 46, controlled by valves 47, 48, 49 and 50, respectively. The flue 42 is connected by passage 51 with the portion 52 of the recuperator 13, which portion of the recuperator is also connected by fflue 53 vto the stack V54. rEhe cold blast main 11 is crossconnected to the hot blast main 18 by means of the passagey 55, this connection being con- The connections for introducing the combustible gases and air for combustion to the stoves may be of any suitable form and have not been shown as they are well known in the art and have no bearing on the present invention.

In the operation of the stoves, normally three of the stoves will be heated by blast furnace gases burned` therein 'while the Vremaining stove is serving to heat the blast air for the blast to the furnace. VVFor example, if stoves 22, 23 and 24 are being heated, valves 38, 39 andV 40 will be closed, disconnecting the stoves fromthe hot blast main, and valves 30, 31 and 32 will be closed disconnecting the stovesfrom the secondary cold blast main 15.

The products of the combustion in the stoves will pass through passages 43, 44 and 45, the

control valves being open, to the .flue 42, and through passage 51 andportion 52 of the `recuperator by. passage 53 to the stack 54. AThese gases will serve toheat any air passing through the other portion 12 of the recuperator.

rPhe fourth stove 25 will be serving to heat the air being sent to the furnace Jfor'blast purposes. `The temperature of this air 'may be controlled in several manners. All of the air will enter -through the cold blast main 11.

'for introduction into the stove. passage 20 with the secondary' cold blast main 15, the passage 20 being controlled by `ature, passing through the passage 29 to the stove 25. By varying the adjustment of valves 16 and 21, any desired proportion of preheated Vair and cold air may be provided The valve 41 will be opened'and the heated air from the stove will pass through passage 37 to the hotblast main 18, The temperature of this air blast may be modified by the admixture of controlled quantities either of air at atmospheric temperature or of air which has been preheated inthe superheater-or of air from both such sources inany desired proportion. It air from the superheater is torbeused-the valve 19 Will be openy any desired amount and this air will pass through passage 1'( to the hot blast main 18.- If air at atmospheric temperature is desired, the mixing valvel 56'may be openany suitable amount and atmospheric air will 'be led from l the cold blast main 11 through passage 55, to the mixing valve and there mixed with hot blast air from the stove or from the stove'and the superheater, if air from Lthe superheater isused.,VVV r It will be apparent that bymeans of our construction` andmethod of operation avery wide control may be maintained over the temperature of the blast air. The stoves may be operated at high efiiciency since the temk1015 perature of the outgoing blast gases from the stove may be high as a further recovery of theheatvof these gases is made in the superheater. This high temperature of the out.- going end of the stove for blast gases per- 1.10 mits the air to be introduced into the stove at an end of the stove which is at high temperature and results in increased heating eiiciency.

`We have shown somewhat diagrammati- -cally one form .of layout suitable for carrying out our invention, but this is to be understood to be illustrative onlyas other constructionsmay ybel kused and We contemplate such changes and modifications as come Withx20 vin the spirit and scope of the appended claims.

We claim: i 1. The methodl of providinghot blast air for furnaces whichcomprises heating a porti'on of the required air to a high tempera- 125 The methodY of providingV hot blast 180 f or furnaces which comprises heating a portion of the required air to a high `temperature7 heating another portion of air to a lower temperature, drawing a third portion of v air from the atmosphere at normal temperature, and mixing said three portions of air in controlled amounts to provide a hot blast of the desired temperature.

3. The method of providing hot blast air for furnaces which comprises heating said airl to a lower temperature7 `further heating a portion of said heated air to a higher temperature, and mixing said` portions of air at higher and lower temperatures in controlled amounts to provide a hot blast of the desired temperature. p

4. The method of providing hot blast air for furnaces which comprises heating said air v to a lower temperature, further heating a portion of said heated air to a higher temperature, and mixing said portions of air at higher and lower temperatures together with aV third portion of air at atmospheric temperature in controlled amounts to provide a hot Y blast of the desired temperature.

5. The method of providing hot blast air` for furnaces which comprises passing the air through a recuperator to raise its tempera'- ture, passing a portion of the air through a stove to further raise its 'temperature7 and mixing air from the stove and air direct from the recuperator in controlled proportions to provide a hot blast of the desired temperature.

6. The method ofproviding hot blast air for furnaces which comprises passing the air throughV a recuperator to raise its temperature, passing a portion of the air through a stove to further raise its temperature, and mixing air from the stove and air direct *from the recuperator together with additional air at atmospheric temperature in controlled proportions to provide a hot blast of the desired temperature.

CHARLES lV. ANDREWS. ALBERT J. HULSE. 

